postinst is in mgetty 1.1.36-3.1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60  | #!/bin/sh -e
case "$1" in
    configure)
        # place the templates in /etc if they're not there ...
        for file in mgetty.config dialin.config login.config; do
	    if [ ! -f /etc/mgetty/$file ] ; then
	        cp -a /usr/share/mgetty/templates/etc/$file /etc/mgetty/$file;
	    fi;
	done
	if [ -n "$2" ] && dpkg --compare-versions "$2" lt "1.1.27-4.1"
	    then
		( for pidfile in /var/run/mg-pid* /var/run/mgetty*
		    do
		      PID=`cat $pidfile`
		      kill $PID
		    done ) || true
	fi
	# Remove old style of crontab insertion if present
	if grep -qs '^#-- mgetty begin$' /etc/crontab
	    then
	    TMP=/etc/crontab.tmp
	    awk 'BEGIN {found=0}
    /^#-- mgetty begin$/ {found = 1}
    /^#-- mgetty end$/ {found = -1}
    {if (!found) print}
    {if (found == -1) found=0}
    END {if (found) exit 1}' /etc/crontab >$TMP &&
	    if [ -s $TMP ]
		then
		mv -f $TMP /etc/crontab
	    fi
	fi
	if [ -f /etc/cron.daily/mgetty ]; then
		rm -f /etc/cron.daily/mgetty
	fi
# Tidy up after cron.daily bug
	if expr "$OLD_VER" : "1.[01].[0-8]-" >/dev/null
	    then
	    echo -n "removing debris from /var/log/mgetty ..."
	    find /var/log/mgetty -type f -name '*.[0-9].*[0-9]*' -print0 | \
		perl -n0e unlink
	    echo done.
	fi
	;;
    abort-upgrade|abort-remove|abort-deconfigure)
	;;
    *)
	;;
esac
chmod 0600 /etc/mgetty/login.config
exit 0;
 |